Signaling system



1939. D. F. JOHNSTON 5+ AL 2,143,560

SIGNALING SYSTEM Filed March 31, 1937 .D. FJOHNSTON INVENTORS-J. B. SH/EL ATTORNEY Patented Feb. 28, 1939 SIGNALING SYSTEM Donald F. Johnston, Glen Head, N. Y.,

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Pelham, and John B. Shiel, gnors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application March 31, 1937, Serial No. 134,004

Claims.

This invention relates systems and more naling systems.

It is the object of this invention to provide,

5 in a telephone system, a simple, economical and reliable arrangement for controlling the time duration of an automatically initiated ringing signal.

This object is attained in accordance with a feature of the invention by utilizing a resistor, having a negative temperature coeificient of resistance, which functions in such a manner as to cause the signaling current source to be automatically disconnected from the telephone circuit a predetermined period of time after its connection thereto.

The invention will be readily understood from the following detailed description made with reference to the accompanying drawing which illustrates the invention as applied to the plug end of a toll tandem trunk circuit employed in extending telephone connections from one toll oifice to another toll ofiice,

The toll tandem trunk circuit T is shown terminating in a plug P at an exchange 0 at which the toll line L terminates in the jack J.

To signal a distant exchange by way of the toll line L, the operator inserts plug P of the toll tandem trunk into jack J of the toll line L whereupon relay 5 operates over an obvious sleeve circuit including the sleeve contacts of plug P and jack J. Relay 5 in attracting its armature establishes an obvious energizing circuit for start relay 6 which relay operates, causing ringing relay 1 to operate in a circuit extending from grounded battery, upper armature and front contact of relay 6, back contact and upper armature of relay 8, conductor 9 to. ground through the Winding of relay 7.

Relay '3 in operating interrupts the continuity of the tip and ring conductors of the toll tandem trunk T and at its lower inner upper armature and front contact connects the ringing current source ID to the ring contacts of plug P and at its upper armature and front contact connects ground to the tip contacts of plug P. Signaling current from the source I0 is therefore transmitted over the tip and ring conductors of the toll line L to effect the actuation of a signal device at the distant exchange to which the toll line L leads.

At contacts 12 and I3 relay 1 connects ground and the ringing current source [0 to the leads [4 and I5 respectively, across which is connected a series circuit including the non-linear generally to signaling particularly to telephone sigresistance l6, winding of relay I! and condenser [8. The resistor I temperature coeflici 6 is one having a negative ent of resistance and in its normal or unheated condition presents a high resistance to the flow of current from the source l0 so that relay I! does not receive sufiicient current to operate.

The resistor I6 may be boron or silver sulphide or any such substance having similar temperature-resistance characteristics.

At its outer lower an obvious circuit the heater coil 2|. the resistor IE to be the influence of th armature relay 1 establishes including resistance 20 and Closure of this circuit causes come heated gradually under e heater coil 2] so that its resistance gradually decreases causing the current from source I relay ll to increase value suflicient to therefore, operates time after the operation of relay 1 the outgoing signal.

operate relay I1.

0 traversing the winding of gradually until it reaches a Relay ll, period of which initiated a predetermined Relay I! operated, causes the operation of relay 8 over an obvious circuit. Relay 8 at its upper armature and back ergizing circuit for contact opens the enrelay 1 which relay thereupon releases disconnecting the signaling current source from the contacts from the toll line L as ductors l4 and I5 circuit for the heater unit 2|. thereupon cools and eventually mal condition.

of plug P and therefor well as from the conopening the energizing The resistor l6 assumes its norand When relay 8 operated, it completed a locking circuit for itself to and lower armature of relay ground on the front contact 6. Relay 8 accordtion as applied to a understood that it in which a timed si toll tandem trunk it will be is applicable to any system gnal is required.

What is claimed is: 1. In a telephone system, a telephone exchange, a line circuit terminating thereat, a source of signaling current, in

cans responsive to the seizure of said circuit for connecting said source of signaling current to said line controlling the disconnection said circuit, means circuit, a relay for of said source from including a heat responsive resistor for controlling the operation of said relay and means for heat ing said resistor.

2. In a telephone system, a telephone exchange, a line circuit terminating thereat, a source of signaling current, in

cans responsive to the seizure of said circuit for connecting said signaling current source to said circuit, a relay for releasing said means to efiect the disconnection of said signaling current source from said circuit, a second relay controlling the operation of said first relay, means including a resistor having a negative temperature coefiicient of resistance for adjusting the time of operation of said second relay with respect to the seizure of said circuit whereby said signaling current source is disconnected from said circuit a predetermined period of time after its seizure and means for heating said resistor.

3. In a telephone system, a telephone exchange, a line circuit terminating thereat, a source of signaling current, means responsive to the seizure of said circuit for connecting said signaling current source to said circuit, a relay for releasing said means to effect the disconnection of said signaling current source from said circuit, a second relay controlling the operation of said first relay, means including a heat responsive resistor for adjusting the time of operation of said second relay with respect to the seizure of said circuit whereby said signaling current source is disconnected from said circuit a predetermined period of time after its seizure and means for heating said resistor.

4. In a telephone system, a telephone exchange, a line circuit terminating thereat, a source of signaling current, means responsive to the seizure of said line circuit for connecting said source of signaling current to said line circuit, a relay for controlling the disconnection of said source from said line circuit, said relay being included in circuit with said source of current and a high resistance element upon the seizure of said line circuit, and means effective also upon the seizure of said line circuit for causing a gradual diminution in the resistance of said resistance element whereby said control relay operates a predetermined period of time after the seizure of said line circuit to effect the disconnection of said source of current from said line circuit.

5. In a telephone system, a telephone exchange, a line circuit terminating thereat, a source of signaling current, a relay responsive to the seizure of said line circuit for connecting said source of current to said line circuit, a second relay, a resistance unit having a negative temperature coefiicient of resistance, said first relay operating also to effect a series circuit including said second relay, said resistance unit and said source of signaling current whereupon the resistance of said series circuit gradually decreases to cause the operation of said second relay a predetermined interval of time after the seizure of said line circuit, and means controlled by said second relay for opening the circuit to said first relay whereupon said relay releases and disconnects said source of signaling current from said line circuit and said resistance unit.

DONALD F. JOHNSTON. JOHN B. SHIEL. 

